This invention relates to dynamic sealing of a shaft and more particularly to a pair of shaft seals with a vent to remove any accumulated fluid between the pair of shaft seals and to prevent the formation of vacuum between the seals and the shaft.
A transfer case connects a transmission with a drive axle for four wheel drive applications or other applications requiring the separation of two fluids. One solution used to solve this problem involves using two different radial shaft seals which are installed around the shaft. If one of the seals fails, fluid accumulates in a cavity between the seals and vents out a hole placed between the seals in the outer periphery of the housing. This solution presents several problems. These include the need to correctly install both seals, the attendant time to install the two seals and the possibility of inconsistent seal depth which may block the vent hole in the housing.
Another solution uses a single metal support structure with a rubber shaft seal with two sprung lips and the outer periphery of the metal structure is partially coated with rubber or alternatively uncoated. This design is prone to cocking in assembly, the formation of a vacuum condition between the two sprung lips and the accumulation of the two fluids between the seals after the seals wear in, or the potential transfer of one fluid to the other fluid which may accelerate failure of the transfer case or the transmission.
Still another solution that has been proposed to solve this problem is to form a dual seal with a venting/drain capability. This design provides a cavity between two L-shaped support members each of which supports a sprung lip seal. The design is also prone to cocking and has a tendency for the seals to be pushed together, preventing the design from draining or venting. Also, this seal design is not compact which is a disadvantage when space is at a premium.
Thus, there remains a need to provide a compact, easily installed dual seal that can be installed in either direction, and that can provide for a controlled radial height to aid in the installation of the seal and assure flow communication between the seals to atmosphere.
The present invention seeks to solve these problems by providing a pair of spaced apart shaft seals in a pair of support members that are connected to form a positive radial engagement surface. The pair of support members also form an internal cavity that is in flow communication with the annulus formed between the pair of seals and through a channel member and the shaft in order to vent to atmosphere. At least one hole at the interface between the pair of seals prevents blocking of the vent in the drain to atmosphere.
The present invention is directed to a dual seal for a shaft. The dual seal includes a first support member and a second support member. A first shaft seal member is adjacent to the first support member. The first and second support members having portions forming an inner cavity and at least one channel in flow communication with the cavity. The second shaft seal member is adjacent to the second support member. The first and second shaft members form an annulus between the first and second sealing members and the shaft. The annulus is in flow communication with at least one hole formed between the first and second seals so that at least one hole permits any accumulated fluid between the first and second shaft seal members to drain into the inner cavity, to prevent the formation of a vacuum in the annulus, and to prevent blocking at least one hole formed between the first shaft seal member and second shaft seal member.
It is an object of the present invention to provide a pair of shaft seal members with a hole between them to prevent the seals from restricting flow out of the annulus.
It is another object of the present invention to provide a compact and easily installed dual seal which keeps two fluids separated and vents vacuum and drains fluid in the annulus between the pair of seals to the atmosphere.
It is still a further object of the present invention to provide positive outer radial interlock of the two support members to maintain radial assembly height and to provide a positive stop for the dual seal during installation.
These and other features of the present invention will become apparent from the subsequent descriptions and drawings.